Propeller



1927 B. u. SEPljLVEDA PROPELLER Filed Jan. 16, 1923 2 Sheets-Sheet 1avwemtg'cl I da 1927' B. u. SEPULVEDA PROPELLER Filed Jan. 16, 1923 2Sheets-Sheet 2 Patented Aug. 23, 1927.

UNITED STATES PATENT OFFICE.

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Application filed January 16, 1923. Serial No. 612,909.

This invention refers to a new form of helical propeller blade, basedupon a theory which when practically applied gives hydraulic and aerialpropellers of greater efficiency than all others heretofore known, ashas been practically demonstrated.

The basis of this propeller, like that of almost all propellers in use,is the helix. The difference between the present propeller and thecommon propellers consists in the distribution of the surface of theblade; the distribution in this propeller being, it might be said, aninversion of that generally used.

It is known that in the common propellersi'nany different forms ofblades are found, the object in each case being to increase itsefficiency, usually by diminishing the prejudicial resistances by meansof the form and disposition of the borders; or seeking a better effectby the transverse adjustment of the propellers surface, it being more ororejudicial resistances,

less curved;"without getting, however, very appreciable differences inthe final result byany of these methods.

When conceiving my propeller, I have not regarded as necessary thediminishing of the a point of really small importance (although I havepaid attention to this factor) but I have proposed to increase the powerby more radical media, and in particular I have tried to facilitate therotation of the blade by distributing its surface in a novel way.

In one of its various mechanical aspects, the blade, as it is known, maybe regarded as'the arm ofa lever, whose power is furnished at its centreof motion, which coincides with the center of rotation of the propeller.The resistance is generated by the fluid in which the blade moves;resistance which is in relation to the surface offered the blade,multiplied by the correspondarm of the lever; or in other words, by thedistance from the centre of rotation. If we consider a blade wide atitsextreme end and narrow at its base, in order to move it with adetermined speed, we should need a power much greater than we shouldneed to effect. the same speed of rotation if we inverted it, or placedits wide end near the centre of rotation.

These considerations include the fundamental idea, the application ofwhich constitutes my invention.

The principal factors which determine ing power consumption of apropeller are its diameter and speed of rotation. The propeller of myinvention turns with much greater speed than do common propellers ofequal diameter, weight, and total blade surface, supplied with the samemotor power, because it presents less resistance to the turningmovement. Consequently, in order to control the speed of rotation of mypropeller so that the number of revolutions will not exceed those of aknown propeller under the same motive power, my propeller must be ofgreater diameter than the known propeller, which greater diameter, ofcourse imparts a correspondingly greater weight. These are conditionswhich are responsible for the advantages in efliciency mentioned above.

The blades form of my propeller, within the fundamental idea previouslyexpressed, and other complementary details contained in the followingexplanation, is illustrated in the accompanying drawings. These drawingsrepresent:

Fig. 1 shows diagrammatically the outline of a blade in front view;

Fig. 2 shows diagrammatically the outline of a blade in side view;

Fig. 3 shows diagrammatically in heavy lines the developed surface of ablade in accordance with the invention, and in light lines the developedsurface of an ordinary blade; 1

Fig. A: is a view of the active face of a propeller embodying theinvention;

Fig. 5 is a side view;

Fig. 6 is a view of the passive face;

Fig. 7 is a view of the active face of a. blade;

Fig. 8 is a section taken approximately along the curved line 12-13 ofFig. 7

Fig. 9 is a section taken approximately along the, curved line 1415 ofFig. 7;

Fig. 10 is a, section taken approximately along the curved 'line 17-18of Fig. 7 f

In all these figures similar reference characters designatecorresponding parts in all views.

As may be noted, the hub 3 is, in proportion, more elongated than incommon proas it is the length of the hub Which re ulatesalmostexclusively the extension 0 the surface.

The border of entrance 6 of the blade is a straight line (1-1, Figs. 1and 2) lying in the plane including the axis of rotation,

and inclined backward at an angle to intersect the circumference 8 ofthe blade at a point opposite, or to the rear of the middle of the hub,at which point it meets the curve '7, which constitutes the border ofexit. This curve 7 approaches from the periphery 8 to the axis ofrotation 11, and all points of the curve lie preferably in a conicsurface produced by the rotation of the line 2-2- about the axis (Fig.2); or they may lie in the plane represented by the mentioned line,(Fig. 2).

The blade sections (Figs. 8,9 and '10) are drawn according to thedevelopment which corresponds to the concentric circles which determinethem for the purpose of indicating clearly the variations of theconcavity and convexity of both faces of the blade.

The active surface of the blade is preferably, generally concave. Ifsections are taken on concentric circles, traced from'the axis ofrotation, the line of intersection with the active surface will be moreor less curved, according to its position towards the end of the blade,except the one that coincides with the surface of the hub, which will bethe only mathematically straight one. This may be observed. in thesections of the blade of Figs. 8, 9, and 10. The greater departure 20(Fig. 9) from the straight line corresponds to the section taken at theWidest art of the blade, decreasing in the remain mg sections bothtoward the periphery and toward the hub to zero at these points.

The blade viewed from the side (Figs. 2 and 5) presents the form of analmost perfeet triangle.

The blades extremity, or the union point 8 of the borders of entranceand exit, must be at a point varying between the middle 9 of the hub andthe posterior extreme 10 of same; but the latter disposition isadmissible only in propellersof great diameter, or with relativelynarrow blades.

The propeller of my invention may .be constructed, as usual, with two,three, or more blades, provided that their width and number will allow acomparatively large space for the fluid to enter.

The width of the blades, as will be understood from the foregoingexplanation,

may be that which is most suitable in each case, taking intoconsideration, as is usual, the numberof revolutions, the diameter, thefluid in which it is designed to work, etc.

As may be observed in Fig. 3 showing a comparison of the developedsurfaces of my propeller blade and one of common type, the concentriccircle 5 represents the path of the centre of gravity of the surface ofthe common blade, or the point of application of the pressures towhich'this blade is subjected; and the circle 4, the path of the centreof gravity of; and point of applicaweaves tion of pressure on the bladeof my invention. As may be seen, this approaches considerably nearer tothe centre of rotation,

.the point at which the resistance is presumed to be applied, reducingtheradial distance, or arm of the lever, which allows agreater speed ofrotation, thus generating a eater impulsion or traction.

rom the foregoing, it will be seen that 4 part to avoid as far aspossible useless resistances. As a result of numerous experiments withbodies moving in different kinds of fluid, ll have observed that it isthe' extreme of the border of exit of these bodies which requires to bemore sharpened or to have a greater obliquity of the, surface in orderto provide the least resistance in proportion to their displacement.

- Reduced to general geometrical terms, the blade form which I haveadopted in this propeller is determined by two planes which cut ahelical surface, namely, a plane 11 (Figs. 1 and 2) which is a radialplane including the axis of rotation, determines the edge of entrance 6;and .another plane, 2-2 (Figs. 1 and 2) perpendicular to the foregoingand which intersects the axis toward the rear of the hub, and intersectsthe edge of entrance 6 at the point 8 which is the tip of the bladedetermining the edge of exit 7 which may be the curved line whichapproaches towards the centre and which we be situated in a planeparallel to that described as determining the border of entrance, andsomewhat advanced in the'di rection of rotation. of the pro ellers asshown in Figs. 11 and 13. Th1s sposition, which does not alter thefundamental prin-, ciples applied by me, will be specially adapted tomeet construction needs of propellers for use in the air.

In order to have the terminal point 8 of i the blade at the desiredradius in relation. to the hub the helical surface should be generatedby a generating line inclined a siliiitable) angle to the axis, as theline, 1-1

The greatest thickness of the blade is not midway between both borders,but is closer. to the border of entrance,as may be observed at 21, 22and 23' (Figs. 10, 9 and 8). This is very advantageous, especially if itis necessary for the propeller at times to function 1n the reversed'lrectlon, because the fact of the greater thickness being near to theborder of entrance, tends to diminish in great part the convexity of thepassive.

surface, and render it more efiicientwhen performing active functions.

As regards the further details of the practical construction, the usualpractice should be followed, of constructing these mechanisms so as tosoften and to round the edges or entering orsalient angles, especiallythe keen edged extremeend of the blade. Which results'from itstheoretical trace. The borders should generally be relatively thin, but

there is no necessity that they end really in an edge.- Especially theborder of exit need only be rounded, approximately to the middle of itslength from the periphery, and may increase in thickness and have abevel cut in the direction of the plane of iotation from there to thehub as indicated by the numerals 12, 161& and 1917 (Figs. 7 8,

end of the hub and intersecting the leading edge at a pointapproximately in a line passing) through .the longitudinal center of the2'. A helical propeller as set forth in claim Lsaid blade having atransverse concavity of unequal depth at different points along itsactive surface.

3. A helical propeller blade as set forth in claim 1, said blade havingits greatest thickness near the leading edge.

AVA helical propeller blade as set forth in claim 1, said blade .havingits greatest thickness near its leading edge and having a transverseconcavity of unequal depth at difi'erent points along its activesurface.

5. A propelling screw, comprisin blades, the propulsive surface or" eachof W ich decreases in a general Way from the hub to- Ward the periphery,the entrance edge of said surface being disposed in a plane passingthrough the axis of rotation, said edge being in a straight line fromsaid axis and the exit edge of said surface commencing at a point in theperiphery onthe hub and lying in a plane at right angles to-said firstplane, said exit edge being curved and contracted in a predeterminedmathematical progression toward the centre, said edges intersecting eachother at a point in a line passing through the longitudinal center ofthe hub.

In testimony whereof I have signed my name to this specification.

BENJAMIN URZE JA Sl.'lllll.VEIIM..

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